PRIOR CONCURRENT THERAPY: Biologic therapy: At least 30 days since prior biologic therapy No other concurrent immunotherapy Chemotherapy: At least 30 days since prior chemotherapy (6 weeks since mitomycin or nitrosoureas) No concurrent chemotherapy Endocrine therapy: At least 30 days since prior endocrine therapy No concurrent systemic corticosteroid therapy Radiotherapy: No prior radiotherapy to at least 25% of bone marrow At least 30 days since prior radiotherapy At least 3 months since prior radioisotope therapy (e.g., strontium chloride Sr 89 or samarium Sm 153 lexidronam pentasodium) No concurrent radiotherapy Surgery: At least 3 weeks since prior major surgery No prior organ transplantation Other: At least 30 days since prior investigational drug No prior therapy that would preclude study No other concurrent investigational drugs No concurrent immunosuppressive therapy